I’ve been all over the internet trying to verify this - thought maybe you guys could help!

I have a 1990 Subaru Legacy LS with an automatic transmission that started failing (won’t get out of first gear). At the same time this started happening, all the dashboard lights, power locks, radio etc stopped working in my vehicle. The mechanic I took it to said that with that make and model of Subaru, when the transmission starts to fail, it actually affects the electrical system, and that it was the transmission causing these electrical problems. I’ve not been able to find anything to either confirm or deny this on the internet… Have any of you guys ever heard of something like this - is it possible? Any help would be great - I’m currently trying to sell this vehicle, and people are staring at me like I’m insane when I try to explain to them that the locks don’t work because the transmission is going bad… Any help?

Distributed processing, a microprocessor in every system on the car, can result in unusual and weird combinations of problems. They are interconnected via a CAN bus. When one of the microprocessors goes berserk it can disrupt communication between all of them. I know of a previous problem where the transmission controller went into jabber mode and tied up the bus enough that the other systems on the car were affected. The owner reported the symptom as possessed locks that would lock or unlock at seemingly random times.

It could be a bad main power wire somewhere in the vehicle. Something similar happened with my Pontiac recently. The transmission, power windows, and heater fan all would quit working at the same time. It turned out to be a bad wiring terminal at the ignition switch.

Rather than saying the tranny is causing trouble to the electrical system I would tend to think it is the other way around. An electrical problem is causing trouble to the areas you mentioned. The tranny is controlled electronically and so a power problem to the controller (TCM) will cause the tranny to have a problem. There is a power panel under the hood and I suspect there is a bad connection with one of the fusible links, in the panel, that is causing this trouble to happen.